difference between "power" and "keyguard"

The 4th button is by default, the "Power" button. If you hit Option+Power, that equates to keyguard, but what really is the difference besides that "locking buttons and touchscreen" message/delay since the "Power" button locks in the same manner ?

You can go to Prefs -> Keygaurd and turn off the autokeygaurd.
This is usefull when you're not going to put it in your pocket and just want to wake it up and do work (without the hassle of unlocking). When you do need to lock it option-power gives the keyguard.

You can go to Prefs -> Keygaurd and turn off the autokeygaurd.
This is usefull when you're not going to put it in your pocket and just want to wake it up and do work (without the hassle of unlocking). When you do need to lock it option-power gives the keyguard.

You could also hold down the power button for a second or two to activate keyguard.